These teachings relate generally to electronic devices, such as mobile terminals, including cellular telephones and personal communicators, and to accessory units for mobile terminals, and more specifically to mobile terminal/accessory interface hardware and software.
Modern mobile terminals, such as cellular telephones and personal communicators, are typically designed with an interface for connecting with external accessory devices. These accessory devices extend the functionality of the mobile terminal and/or provide other useful functions. Examples of accessories include battery chargers, headsets and xe2x80x9chands freexe2x80x9d adapters (enabling the mobile terminal to be used without being held in the user""s hand).
As can be appreciated, as the complexity of mobile terminals and their accessories have increased the required mobile terminal/accessory interface has increased in complexity as well. For example, the interface is typically required to accommodate the transfer of data between the mobile terminal and the accessory.
It is desirable that the mobile terminal/accessory interface be physically and electrically robust, be capable of handling low error rate data transfers, and yet still be low cost and of minimal complexity. Another important consideration is the power consumption of the mobile terminal/accessory interface. As in all battery powered devices, the minimization of power consumption is an important goal.
When using conventional accessory interfaces it has been problematic for the mobile terminal to detect certain specified accessories. Problems have also been observed using analog to digital converter (ADC)-based accessory detection schemes. Furthermore, with the ADC-based detection scheme there are only a limited number of accessories that can be identified (limited at least by the precision of the analog voltage that is produced to represent a given accessory, and by the conversion accuracy of the ADC in the mobile terminal).
Prior to this invention, all of the foregoing various and somewhat conflicting needs and goals have not been realized in circuitry that provides a mobile terminal/accessory interface, and the foregoing problems have not received a satisfactory resolution.
While described above in the context of mobile terminals, it should be appreciated that the same or similar problems can exist in other types of equipment.
The foregoing and other problems are overcome, and other advantages are realized, in accordance with the presently preferred embodiments of these teachings.
An Accessory Control Interface (ACI) encompasses an interface protocol and an accessory application specific integrated circuit (ASIC) that together provide an ability to identify, authenticate and control the operation of accessories used with a mobile terminal. In the preferred embodiment the ACI ASIC is installed within the accessory, and communicates through an input/output port and associated connector with circuitry in the mobile terminal.
Through the use of the ACI ASIC the mobile terminal is enabled to recognize when an accessory is inserted or removed. Preferably a mobile terminal interrupt signal line is activated by the ACI ASIC for interrupting the data processor of the mobile terminal. For example, when the mobile terminal is placed within a hands free (HF) stand the mobile terminal is automatically switched to the HF mode. When the mobile terminal is removed from the HF stand the mobile terminal is automatically switched out of the HF mode and back to the normal mode of operation. The ACI ASIC enables the interface to identify different accessory types by parameters stored as digital data within a memory of the ACI ASIC, and transferred to the mobile terminal using a serial data bus.
An important feature of this invention is the power savings that are realized, since after insertion detection is accomplished (the mobile terminal and accessory are physically and electrically coupled together) subsequent communications can be performed at a rate set by the low speed (e.g., 32 kHz) mobile terminal sleep clock. The sleep clock is one used to periodically interrupt the mobile terminal to exit a low power, idle mode of operation. This technique provides considerable savings in mobile terminal (and accessory) power consumption.
Another important feature is that the ACI ASIC includes or is coupled to a simple and inexpensive local oscillator that is implemented as an RC oscillator, as opposed to a crystal oscillator. This is made possible by the tolerance of the interface to the potentially wide frequency range (e.g., 20 kHz to 60 kHz, nominally about 27 kHz) and inaccuracy of the accessory RC oscillator (+xe2x88x9250%). The RC oscillator can be integrated into the ACI ASIC, thereby realizing considerable cost and circuit area savings, as well as improving the reliability and testability of the accessory and accessory interface.
A further advantage made possible by the use of this invention is the ability to design and offer new accessories, even for those mobile terminals that are already in the field. This is possible because the accessory is enabled to inform the mobile terminal of its relevant features due to the presence of a non-volatile memory within the ACI ASIC, where the memory stores feature data that is readable from the mobile terminal through the interface.
As will be shown below, this invention provides an interface between a master device and a slave device. The interface includes a bit serial bidirectional signal line for conveying commands and associated data from the master device to the slave device, and for conveying a reset signal, an interrupt signal, and a learning sequence signal for specifying a duration of a bit time for data transferred from the slave device to the master device. The bit serial bidirectional signal line further indicates an accessory device connected/disconnected state to the master device.
In the preferred embodiment the master device is or includes a mobile terminal. The mobile terminal samples the data transferred from the slave device to the master device in synchronism with its sleep clock. The interface includes, in the accessory device, an Accessory Control Interface chip and an on-chip RC oscillator providing a clock signal to the Accessory Control Interface chip. The bit time is a multiple of the clock signal, and the mobile terminal adapts the sampling of the data transferred from the slave device in accordance with the specified duration of the bit time.
The Accessory Control Interface chip further includes an on-chip non-volatile memory for storing at least accessory related feature data that is readable by the mobile terminal in response to a memory read command sent from the mobile terminal to the Accessory Control Interface chip over the bit serial bidirectional signal line.
The Accessory Control Interface chip further includes an on-chip challenge/response authentication function that is challenged in response to an authentication challenge command and associated challenge data sent from the mobile terminal to the Accessory Control Interface chip over the bit serial bidirectional signal line. Authentication result data is subsequently sent by the Accessory Control Interface chip to the mobile terminal over the bit serial bidirectional signal line in response to an authentication result command sent from the mobile terminal to the Accessory Control Interface chip.
While described herein in the context of a master device, or a mobile terminal, such as a mobile voice terminal such as a cellular telephone, this invention applies as well to personal digital assistants (PDAs) and other handheld or otherwise portable devices that are intended to be interfaced to external equipment, devices and/or accessories. As such, hereafter the term xe2x80x9cmobile terminalxe2x80x9d, and also the term xe2x80x9cmaster devicexe2x80x9d, should be interpreted so as to include a wide variety of equipment types, both portable and non-portable, that include, but that are not limited to, cellular telephones, personal communicators, personal organizers, personal digital assistants (PDAs), email terminals, personal computers, laptop computers, notebook computers, workstations, home electronic devices, including game consoles as well as television monitors, and other devices that can be interfaced to external equipment, devices and/or accessories.